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Structure in Thin and Ultrathin Spin-Cast Polymer Films
1C. W. Frank, V. Rao, and M. M. Despotopoulou are in the Department of Chemical Engineering, Stanford University, Stanford, CA 94305-5025, USA. R. F. W. Pease is in the Department of Electrical Engineering, Stanford University, Stanford, CA 94305, USA. W. D. Hinsberg, R. D. Miller, and J. F. Rabolt are at the IBM Almaden Research Center, IBM Research Division, 650 Harry Road, San Jose, CA 95120-6099, USA.
Ultrathin polymer films exhibit altered molecular organization and thermophysical properties compared to bulk polymers. Spin-casting amorphous poly(3-methyl-4-hydroxy styrene) and semicrystalline poly(di-n-hexyl silane) revealed thickness-dependent behaviors.
Area of Science:
- Polymer Science
- Materials Science
- Physical Chemistry
Background:
- Molecular organization in polymers significantly impacts thermophysical properties.
- Ultrathin and thin polymer films exhibit unique behaviors distinct from bulk polymers due to geometric constraints.
Purpose of the Study:
- To investigate the influence of constrained geometry on the molecular organization and thermophysical properties of ultrathin and thin polymer films.
- To compare the behavior of amorphous poly(3-methyl-4-hydroxy styrene) (PMHS) and semicrystalline poly(di-n-hexyl silane) (PD6S) in thin film formats.
Main Methods:
- Fabrication of ultrathin ( < 1000 Å) and thin (1000–10,000 Å) polymer films using spin-casting.
- Analysis of amorphous PMHS and semicrystalline PD6S films.
Main Results:
- Ultrathin PMHS films show higher residual solvent content, suggesting enhanced glass transition temperature due to stronger hydrogen bonding.
- Crystallization in ultrathin PD6S films is hindered, requiring a critical thickness of 150 Å for crystalline morphology.
- PD6S crystallization rate in ultrathin films is initially slow, accelerating as thickness approaches 500 Å.
Conclusions:
- Film thickness critically influences polymer molecular organization and thermophysical properties.
- Geometric confinement effects are pronounced in ultrathin polymer films, altering properties like glass transition and crystallization.
- The study highlights the importance of film thickness in designing and utilizing polymer materials for specific applications.